1. Field of the Invention
The present general inventive concept relates to a 3D image display system, and more particularly, to an image displaying unit of a 3D image system having multi-viewpoints, in which 2D and 3D images are interchangeable.
2. Description of the Related Art
A three-dimensional (3D) display can be classified according to a 3D display method, viewpoints, view conditions, observation conditions, whether or not an observer wears supplementary glasses, and the like. Binocular parallax is widely used to allow observers to recognize displayed images stereoscopically. If an observer's eyes receive images that are observed from various angles, the observer can perceive a sense of space through the observer's brain operation. A method of displaying a 3D image is generally classified into stereoscopic display and volumetric display based on recognition of stereoscopic vision.
In the stereoscopic display, two pieces of a two-dimensional (2D) image having binocular parallax are provided to right and left eyes, thereby recognizing whole images stereoscopically. In the stereoscopic display, since right and left images that are taken from the two eyes are displayed, the stereoscopic display has a disadvantage in that 3D images are recognized only from a single direction.
In the volumetric display, stereoscopic images in which an object is taken in various directions are displayed. Thus, the volumetric display has an advantage in that 3D images are recognized from various directions.
A multocular image displaying method, which is one of 3D image display methods, is a technique of displaying binocular parallax images that are taken in various directions, and includes a parallax panoramagram method, a lenticular method, an integral photography or volumetric-graph (IP) method, and a slit scan method.
Among these methods, the IP method does not require additional glasses for observation. Also, the IP method is very useful to create 3D video because it can obtain stereoscopic video automatically in desired positions. A display using the IP method includes a micro lens array or a pinhole array and is widely used in many applications, such as medical science, engineering, and simulation.
FIG. 1 is a schematic view of a conventional 3D image system (hereinafter, referred to as a conventional system) using IP method.
Referring to FIG. 1, the conventional system includes first to third micro lens arrays 111, 113 and 114 and a TV pickup tube 116. The micro lens arrays convert an image taken by a camera into a 3D video signal. An optical diffusion layer 112 is interposed between the first and second micro lens arrays 111 and 113 and is attached therebetween. The second and third micro lens arrays 113 and 114 are spaced apart from each other by a predetermined distance. The first to third micro lens arrays 111, 113 and 114 are fly eye lenses. A photo-sensitive layer 115 is interposed between the third micro lens array 114 and the TV pickup tube 116.
The 3D video signal passing through the first to third micro lens arrays 111, 113 and 114 and the TV pickup tube 116 is transmitted to a receiving unit 118 through a transmitting unit 117. The 3D video signal transmitted from the transmitting unit 117 is received by the receiving unit 118 is then transmitted to a display unit 120. The display unit 120 is configured to display the transmitted 3D video signal. The display unit 120 includes a display 120a, a fluorescent screen 120b, and a fourth micro lens array 120c attached to the fluorescent screen 120b. The fluorescent screen 120b is interposed between the display 120a and the fourth micro lens array 120c and is attached therebetween. The fluorescent screen 120b displays an image corresponding to the 3D video signal. A viewer stereoscopically views the displayed image through the fourth micro lens array 120c. The image that is formed on the fluorescent screen 120b is identical to the image that is formed on a photosensitive layer 115 of the TV pickup tube 116 through the first to third micro lens arrays 111, 113 and 114. The fourth micro lens array 120c has the same structure as the third micro lens array 114. Relation of the display 120a to the fourth micro lens array 120c is identical to that of the TV pickup tube 116 to the third micro lens array 114. Thus, viewing the image that is displayed on the fluorescent screen 120b in front of the fourth micro lens array 120c, a viewer recognizes virtual stereoscopic video of an actual object.
Meanwhile, simulation or medical analysis systems require a 2D image as well as a 3D image.
The above-described conventional system, however, is exclusively used for 3D image implementation, so that selective implementation of 2D and 3D images is impossible. Accordingly, application of the conventional system is very limited.
Also, the micro lens array provides vertical and horizontal parallax at the same time and displays volumetric images, but must record a whole image of an object on one micro lens. Therefore, it is necessary to develop a display device that can display a whole image of an object on an area corresponding to a diameter of the micro lens in standard resolution. However, it is difficult to make the micro lens array having a high resolution.
Further, image discontinuity may be caused due to a gap between micro lenses.
Furthermore, distortion or deflection may occur at boundaries that are formed between micro lenses, causing ghost images in which 3D images overlap with each other in 3D image implementation.